GROWTH OF PLANTS.

Globe, Volume XXIII, Issue 2196, 10 March 1881, Page 3

GROWTH OF PLANTS.

The following racy article, suggested by a recently published work by Mr Charles Darwin on the mode of plant growth, appeared in a late number of the London " Daily Telegraph " : Cabbages are not the silly things that moat peoplo suppose them to be. At any rate Dr Darwin, in his new work on plants, puts us on our guard against the risks we run by supercilious depreciation of even our humblest vegetables. The trodden worm, we all know, will turn —though it does not do itself much good by turning, after all—and the longBuffering cabbage and the half-hearted parsnip may some day, when we are least expecting it, join the head-strong onion and furious horse radish in a goneral aisault upon the human race. The horrors of a vegetable revolt can hardly be over-estimated. Indeed, if the contents of Coveut Garden market were one of these mornings to run amuck among the horticultural population the consequences might be ve.-y considerable. A cart-load of determined carrots would be a serious assailant, and the police would have a troublesome task of it to rescue a bystander if he were beset by a birrowful of mangold wurtzels. Nor is such a catastrophe as an insurrection in our nursery gar-

dens beyond the possibilities of botanical science, for if Dr. Darwin is correct—and he is seldom wrong—there is no knowing what plants may do in time. Already we find from that distinguished inquirer's latest volume that vegetables are by no means the " inanimate" things we have hitherto thought them, and that they indulge in a great variety of movements, which are regulated not by any blind laws, but by the impulse or sensation of the moment. If the sun be let in suddenly upon their roots they shrink away from it; if they are tickled with a feather they giggle; if touched with caustic they jerk to one side. Take the liberty of handling some of their leaves, and they at once shut up, and pretend to sleep, as if they had not noticed the rudeness ; irritate others and they become greatly excited. All these movements, we are told, are modifications of the great principle of " circular nu- | tation," and further modifications may be gradually acquired by natural eolection. This I " circular nutation " is a capacity for spiral motion, which it has been discovered all parts of plants possess, and which they are perpetually exercising from tho sprouting of the seed to the maturity of the tree; and circumstances might therefore occur which would change this normal revolving movement into others more eccentrio and possibly disagreeable. Turnips, for instance, might suddenly take to whirling themselves round and round, so that it would be impossible to grow them on sloping ground, as their violent revolutions would soon twist them out of the earth, and the whole fieldful of roots would come rolling down hill together. Or an avenue of trees might nutate so outrageously that it would be dangerous to pass under them, while their roots, all working together like so many infuriated corkscrews underground, would keep our roadways in perpetual commotion.

In the meanwhile, there is no immediate cause for anxiety, for plants have not as yet done anything more extraordinary than nutate within their proper circles. Still even thus the amount of vegetable movement which is constantly going on around us is almost too prodigious for complacent contemplation. No sooner does the seed sprout thau the little radical, or rootlet, begins to twist round and round, making an animated gimlet of itself to bore a hole in the earth. Having pierced the surface it still continues to work its way down in ovals, gradually getting deeper and thicker and stronger. Long before this the stem also has sprouted from the seed, and it too has begun to gyrate, working its way up into the air by a series of ellipses, jerk by jerk, and every leaf it throws out, and each part of every leaf as it appears, commences at once in the same way to rotate. As a matter of fact, therefore, the earth on all Bides of us is filled with roots that are continually screwing themselves through the soil, while all the branches overhead, and all the twigs upon the branohes, and all the leaves upon the twigs, are for ever describing little circles as they grow. Why they do it no one knows, not even Dr. Darwin; but he described the process of movement as being caused by the unequal expansion of the cells on the one side of the part affected or the other, causing '' a minute earthquake "in the plant. But whatever the reason for it, the utility to the vegetable of constant "circumnutation " is undeniable, for vegetables, unlike men, never do anything that is not good for them. In climbing plants it manifestly helps the creeping parte immensely, while in others it gives every side of the leaf a fair share of all the different conditions of the surrounding atmosphere. That the roots benefit by this spiral method of progression it is hardly necessary to say, or else we might wonder at carpenters for using a gimlet, or at ourselves for buying oorksorews. There is, however, a far more significant side to this curious habit of the plants about us, and that is the relation which " circumnutation" bears to the voluntary movements of animals. Where, indeed, are we to draw the line ? When light strikes one side of a plant, or light changes into darkness, or when gravitation acts on a displaced part, the plant is at once enabled to move either to or from the exciting cause, just ae suits its welfare best; and when night comes on the vegetables go to sleep. This is no figure of speech, for the sleep of plants is a very real thing indeed, amounting in many cases to a temporary suspension of all aotivity and the enjoyment of complete repose. They tuck their leaves round them, bend down their heads, and go fast asleep. Perhaps even they snore sometimes. It is not, however, during their sleep that the vegetables of our fields and gardens resemble the lower orders of animals most closely, but during their waking hours, and Dr. Darwin's experiments will go far to assure the world that the plant hag a brain. Its brain, curiously enough, is in the tip of the root, but the position of that important organ matters little so long as it performs its functions properly. And nothing oould exceed the admirable punctuality and precision of the brain-tip in the roots of plants. If it be pressed or wounded, it immediately transmits an influence to the parts above it, which at once begin to move this way or that; and more than this, it can distinguish between a hard substance pressing it on one side and a softer one on the other, for it immediately warns the rest of the root to keep to the softer side. The whole prosperity of the plant, in fact, depends upon the sagacity and vigilance of the brave little pioneer tip, and all the larger portions obey with punctual exactness the directions telegraphed to them from this oentre. It pushes its way, corkscrewing as it goes, through the soil, and keeps on calling out as it were to the rest of tho root to tell it which way to turn for most moisture, and which way for most light. " Look out," it cries, " for a big stone on the left," and the root looks out accordingly ; or again the •lismal news comes up the trembling radicle that a slug is eating the tip off, and the plant at once sends down another brain-feeler to replace the leader that is being consumed. What serious difference is there in this behaviour to that of the lower animals, the curious creatures of sea life, which are hardly one thing or the other, and where are we to draw tho line of vegetable possibilities ?

We know already from Dr. Darwin's book that the tip of the root has learnt all its wisdom from experience, that it is the most advanced portion of the plant, and represents all that is enterprising and intelligent in the vegetable. But eduoation, after all, gradually spreads from class to class, and just as in time we hope to see Hottentots fit to sit in Parliament, and to have Bosjeman dons in our universities, so in time the other portions of plints may become educated and ambitious, acting independently, with increased vigor and unerring judgment. At present the root tip is most discreet in its conduct, for it gimlets its way patiently and unobtrusively through the soil, in search of such nourishment as the plant whioh it has to look after stands in need of. In time, however, the vegetables may, with better information, beoome more daring ; and who can say what may happen ? How will the farmer keep his crops from making straight for the nearest manure heap, or how, indeed, in inclement weather, shall we restrain our shrubs from ooming into the house for shelter ? Already we have oarnivorous plants which oontent themselves with insects, but suppose the taste spreads, and man-eating trees are developed " by natural selection? " It would be dangerous then to walk alone in a shrubbery of robust plants, and he would be a very bold man indeed who ventured without weapons into Epping forest. Wo have all heard children speak of_ the_ trees that seemed to them, especially in_ the night, to wave their arms about in a theatening manner in front of the house, and to look in mockingly at them through upper - storey windows ; but if the worst that is now threatened really befalls, we shall have to keep our windows strongly barred to provent the poplars from ooming into the nursery, and look the garden gate at night to prevent the ravening laurels from getting out into the streets. With the same amount of intelligence that the root-tip now possesses diffused in an equal, or it may be greater, degree over the whole plant, we shall require no microsoope and none of the smoked glass diagrams which Dr. Darwin now employs to observe and record their motions; for the botanical world will be in constant and manifest tumult, our gooseberry bushes struggling with eaoh other, and our cabbages at open fisticuffs. A horsewhip or a bludgoon will be among the gardener's ordinary tools, and little children will never be allowed to go near any of the unohained plants. The intelligent turnip, when it sees the cook coming, will pull itself out of the ground and bolt off the premises, and carrots will require as much catching as larks. In the meanwhile, as we have already said, the plants are not outrageous in their revolutions, and people, therefore, may set to work at their Obristmas trees without any apprehension of th>»e vegetables circumnutating too violently to 1)0 properly ornamented.